Chill cast iron alloy



Patented Jan. 22, 1935 v UNITED STATES CHILL CAST IRON ALLOY Paul D.Merica, New York, N. Y., and James S. Vanick, Elizabeth, and Thomas H.Wickenden, Roselle, N. L, asslgnors, by mesne assignments, to TheInternational Nickel Company, Inc., New York, N. Y., a corporation ofDelaware No Drawing. Application October 21, 1926, Se-

rial No. 143,293., Renewed June 13, 1934 3 Claims.

This invention relates to alloys and more especially to chill castnickel bearing iron alloys.

The invention relates particularly to castings formed by casting nickelbearing iron compositions against chills to form castings having extremehardness in the chilled portion and improved toughness and strength inthe chilled portion and in the gray iron adjacent the chilled portion.This material is well adapted for chilled Percent 24 .25-2

Carbon Silicon Manganese .25-2 Nickel 2 -10 Chromium Up to 4 25Phosphorus and sulphur may be present within the ranges usually found incast iron, as for instance phosphorus .03 to 1.15% and sulphur .03 to25%. See any edition of Kents handbook, 1900 and later; Moldenke,Principles of Iron Founding, edition of 1917, page 198; Hatfield, CastIron In The Light of Recent Research; and others. In respect to theranges of phosphorus and sulphur in chilled, white and gray ironcastings such as for rolls, cams, brake shoes, gears, plow points, etc.,phosphorus ranges from, under .10 to 1.0% and sulphur .04 to 25%. See,particularly pages 196, 182, 183, 199 and 198 in their order ofMoldenkes Principles of Iron Founding, 9 1917, where both the phosphorusand sulphur for chilled rolls must be, under .3 and .08% respectively,and for chilled castings in general. As indicated on page 183, thephosphorus and sulphur shall be, below .20 and .06% respectively. Onpage 199, it is shown Again, the sulphur and phosphorus percentagesgivenexcept where wanted high, can be anything below the figures. Inaddition, page 198, there is a statement as to the percentages in thetables on the pages noted that The tables of analyses given in the aboveclassification of castings must, as was said at the outset, beconsidered only as typical. Again, in Kents Mechanical EngineersHandbook, edition printed in, 1923, attention is called to page 434,wherein sulphur is recited from .05 to 20%, and

(Cl. I5-1) it states in the lower part of that page and in respect tothe above sulphur contentIn this composition phosphorus is supposed tobe well below .10% It is also to be noted that the ranges of analyses ofAmerican, as well as foreign, pig irons, are good indications ofcastings produced from pig irons as very often a definite and consistenttype of pig iron mustbe used. Such ranges are to be found in Appendix IIof Hatflelds Cast Iron in the Light of Recent Research, second edition1918 and third edition 1928.

The composition may be varied somewhat, if desired, by the addition of'other alloying materials, such as molybdenum, tungsten, titanium,copper, etc. The carbon content is within the general range usual forcast iron, from either air furnace or cupola.

Casting compositions lying within these ranges are particularlydesirable in that good adjustment of nickel, chromium, silicon andcarbon contents is secured to nicely regulate thedepth of chill.

We find that the amount of chill in the chill cast iron may bemaintained sensibly constant if nickel and chromium are added asalloying materials' in about the ratio of 2 or 3 to 1, say about 2%,to 1. We also find that the amount of chill may be nicely controlled bysuitably adjusting the various elements according to the rough rule that1 part carbon equals 3 silicon, 1 part silicon equals 2 parts nickel, 1partchromium equals 2 parts nickel, and 1 part sulphur equals 10 partssilicon; increasing the silicon, carbon and nickel acts to decrease thechill, whereas, increasing the chromium and sulphur acts to increase thechill.

The silicon and carbon contents may be lowered, if desired, by using ahigher ratio of nickel to chromium thanthat mentioned above, theincreased chilling tendency accompanying the lowered'silicon and carboncontents being counteracted by the higher nickel content.

For ordinary work, however, we have obtained good results with acomposition containing about the following percentages:

Percent Carbon 3.0 Manganese .6 Silicon 1.0 Nickel 4.5 Chromium 1,5

Phosphorus and sulphur be present within the ranges usually found incast iron as indicated above.

Such a composition, ii. chill cast, will give a white iron having aBrinell hardness of 550, as compared with the 400-500 of ordinarychilled iron. The chilled metal under tension has a transverse strengthof 8000 pounds for 1%, inch square bars tested on 12 inch centers incomparison with about 6000 pounds for ordinary high carbon chilled iron.Gray iron having this composition has a tensile strength of about 35,000pounds per square inch in comparison with 20,- 000 to 25,000 psi forhigh carbon iron ordinarily used for chill work.

Our composition has the further advantage that it is subject to heattreatment and the hardness and toughness may be so modified, if desired.

The composition is not only extremely hard in the chilled condition, butit is strong and tough both in-the chilled condition and in the graycondition. These characteristics render the composition desirable forchilled castings to be subjected' to heavy pressure or impact, sincesuch castings are less liable to breakage than ordinary chilled ironcastings.

We are aware that nickel has been proposed as an addition material toreduce the chilling e1- i'ect in iron alloys, and that chromium has beenproposed as a hardener. We have found, however, that a proper proportionshould be maintained between the nickel and chromium with respect to thesilicon and carbon if the composition is to be rendered hard, and yettough and strong. By properly proportioning the alloying elements, wehave produced an improved iron alloy adapted to be chill cast to form anexceedingly hard and tough white iron with a strong, tough gray ironadjacent thereto.

We have found that the hardness of chilled cast iron castings made underour invention is due to the fact that the matrix portion of the iron ischanged from the softer pearlite of ordinary chilled iron castings intothe harder martensite or troostite. Martensite is often associated withaustenite and hence by martensite, we mean martensite or austenite orboth in association. Hence the resulting hardness is between that of thevery hard iron carbide grains and the martensite giving a Brinellhardness 01' from 550 up to about 750 where the carbon is about 3.50%.

This hardness may be regulated somewhat by proportions of the alloy orthe use of equivalents.

A further important advantage of our invention resides in the provisionof an improved chill casting alloy wherein the depth of chill may benicely controlled by suitable adjustment of the addition elements.

Cast iron of our composition may be made either in the air furnace orcupola. and we intend to cover such composition of cast iron made ineither type of iumace.

.We claim:

1. A chilled iron casting containing carbon 2-4%, silicon .5-l.25%,nickel 3.5-6% and chromium .5-2% the nickel content being greater thanthe chromium content.

2. A chilled iron casting containing carbon 2.5-3.3%, silicon .5-1.25%,nickel 3.545% and chromium 5-2%. r

3. An iron roll containing carbon about 2% to 3.75%, nickel about 3% to8%, chromium about 1% to 3%,. sulphur not over about .10%. phosphorusnot over about .40%, and manganese less than 1.5%.

PAUL D. MERICA. JAMES S. VANICK. THOMAS H. WICKENDEN.

